In the electric water heater manufacturing technical field, most pressurized type electric water heaters can be directly connected to the main water supply with pressure, their structure usually use stainless steel and soldering to a sealed container as internal tank body, then install water inlet pipe, water outlet pipe, exhaust pipe and electric heating pipes, mounting safety valve on exhaust pipe, and stainless steel sealed container's outside has heat insulating protection layer and shell. If use this kind of electric water heater structure as heating and drinking water supply to people, there are some problems following. Firstly, the stainless steel soldering material can pollute water in the container, make water's drinking quality worse, secondly, the hermetical stainless steel container cannot be cleaned, after long time use, lime scale will be accumulated and affect water quality. Thirdly, if safety valve on the exhaust pipe does not work, it could cause use safety problem. Finally, sealed stainless steel container is difficult to manufacture, slow speed to produce and with high production cost.